weeks or even months ago, “car mode” started to seemingly randomly get enabled

ever since, that seemed to happen more often

at some point, when you made or received a call, the speakerphone would sometimes be automatically turned on

since a while, when you make or receive a call, the speakerphone is always automatically turned on

since then, when connected via Bluetooth to a speakerset, you can change the volume on your phone up or down but that won’t have any effect

it drives you crazy

If any of these apply, I probably have the solution. I’ve had this exact problem since months now, and tried a few things that the interwebz suggested, but none of it would help. Understandably so, because it has nothing to do with Android, nor HTC, Samsung, or any other phone selling company, or software maker.It is a design flaw in the micro USB architecture – and at that level is where you can solve this problem within 5 minutes

Micro A or B USB, commonly known as micro USB, is the official name for the connector on most non-Apple phones. A picture of mine (a micro B USB) is on top of this post.
What is inside the phone is called receptacle.
What plugs into that, is called a plug

If you use your phone heavily, you might end up charging it (perhaps not completely, but at least plugging it in in order to charge it) 5-10 times a day; I know I do. It all depends on how many locations I am at on a daily basis. Being somewhere near a power outlet for a while? Plug it in!
So, after roughly a year, I had plugged a micro USB connector (we have many) into my phone roughly 2,000 times.
What happens when you rub iron against iron over a prolonged time period? Look at the hinges of your doors, and you’ll probably see those little black specks on the side and below them. If you put your finger on them, you’ll find that they feel – like oil, greasy.
You can rub them between your fingers, and leave a black smear

Well, the same thing has happened inside the micro USB connector on your phone – it contains little black specks of what I call iron smear. The iron smear acts as a conductor and somehow gives your phone the idea that it has a connector plugged in into its micro USB receptacle – and more

If you remove the smear, you’ll have your old phone back. No more speakerphone, no more car mode, you can adjust audio volume over Bluetooth, and you’ll be a lot less reluctant to either make a call or receive one

Now, if you take a close look at the micro USB receptacle, you’ll see that it is of a very fragile nature. The very thin piece in the middle actually connects to the 5 wires inside, so if you lose that, you lose it all – including your phone. So be very, very careful (and read the disclaimer on top of this post again)

How can you clean the “iron smear”? With an ordinary piece of paper. Let me just tell you how I did it, and you be the judge of what you’ll do next

I took a blank sheet of paper

I folded it, flattened the crease by using my nails, and tore off a piece the size of my pinky finger

I folded one side of the bottom, flattened the crease, and did the same to the other side: I got myself a “phone-pick” (see below)

I powered off my phone, took out the battery (one can never be careful enough) and started “picking my phone” very carefully by sticking the paper into the receptacle and gently moving it back and forth

After 10-15 seconds, I took it out, and looked at the paper: it had black smudges at the very top!

I tore off the top, did some folding and crease sharpening again, and repeated the process

I repeated the last step until the piece of paper wouldn’t get black smear on it anymore

My phone pick

I put the battery back in, powered on the phone, and made a call. The speakerphone didn’t turn itself on automatically!

I connected it to a speaker over Bluetooth: I could adjust the volume again!

I plugged in the adapter to see what happened when charging the phone. The car mode didn’t get turned on!

I was happy. I now clean the micro-USB receptacle on my phone every 2-3 months – and stay happy!

[Disclaimer: this information is provided ‘as is’ without warranty of any kind. Use at your own risk]

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Founder of We Wire People, Martijn has 15 years experience in the field of Integration, as an Architect working in and for Enterprises. He mainly advises in case of mergers, application rationalization and Cloud / Social Media back-office integration
Martijn blogs at martijnlinssen.com

Thanks! This worked for me. I was having the “can’t adjust the headphone volume” problem.

After cleaning the USB port the phone still enters car mode if I wiggle the connected USB cable, but it always exits car mode when I unplug. Before it would often stay in USB mode and cause problems, even after disabling car mode (by clicking the notification).

There is a way to fix the car mode problems without rebooting the phone, when the phone is stuck in car mode, or even after disabling car mode (which doesn’t fix the volume problem). Plug the USB cable back in and wiggle it until car mode turns on again, if necessary, and then off. I.e., the big problem is when you unplug the phone and it remains in (even partial) car mode. A lot of reboot before I figured this out.